Field Of The Invention
This invention relates to the field of gas compressors used in aeropropulsion systems which involve compression of atmospheric air, mixing with fuel and releasing energy in a combustion process to propel a vehicle by means of the resulting thrust.
Most jet propulsion systems rely on turbine machinery to produce initial compression of the inlet air stream. Such systems compress atmospheric air with either axial or radial flow compressors, driven by exhaust products of the combustion process expanding through either radial flow or axial flow gas turbines. These compressions and expansions may occur in several stages, requiring shaft linkage to connect the stages. To protect the turbine components from thermal destruction, limitations are often placed on the temperature of the combustion process through the use of large quantities of excess air, resulting in lower efficiency in terms of fuel consumed versus thrust produced, larger sizes and higher weights, than if higher temperatures were used in the combustion process. Additional safeguards against thermal destruction include the extensive use of alloys containing strategic materials resistant to the high temperatures found in such environments. Such turbine equipment is necessarily complex, resulting in high manufacturing and maintenance costs.
The ram jet is another configuration which is used. In the ram jet, the incoming air is compressed by the relative motion between the atmosphere and the propelled vehicle. This compressed air is then mixed with fuel and ignited, producing thrust. The disadvantages of this system include the fact that the propelled vehicle must be in motion before the engine can be started. In addition, engine efficiency decreases substantially at speeds below Mach 1.5.
Still other configurations of jet engines combine the turbine and ram jet principles, using the turbine compressor at low speeds and ram jet compression of inlet air at high speed. These composite systems do not solve the problems, however, of excess weight, mechanical complexity, high temperature, or low speed operation, all of which are addressed by applicant's invention.
For many years, devices have been in use whereby the stagnation pressure of one gas stream is increased by dynamic interaction with a second gas stream moving at high velocity. Most of these devices are designed so that the driven gas stream interacts with the driving stream at sonic or subsonic velocity, severely limiting the pressure ratio achievable at acceptable mass flow ratios. Some devices utilize supersonic interactions instead. These devices perform adequately when the differences in stagnation temperatures and enthalpys between the two gas streams are small. If, however, the driving gas stream is much more energetic than the driven stream, a sharp drop in pressure ratio is observed. Typically, airborne sources of driving gases are high in temperature and enthalpy compared to ambient conditions. The result is a low overall system pressure ratio while at zero or low forward velocity, with attendent high specific fuel consumption, and low thrust.
Typical of prior art arrangements are the devices disclosed in U.S. Pat. Nos. 2,920,448, 3,323,304, 3,374,631, 3,382,679, 3,750,400, 3,800,529, 3,800,531, 4,379,679. Also of some relevance is French Pat. No. 2,534,983.